The present invention relates to an upper structure for a shoe, and more particularly, to an improvement in the structure for enhancing a fit of a heel portion of the shoe during heel contact of the shoe with the ground to the push off motion of the foot.
A shoe is generally composed of a sole, an upper that is fixedly attached on the sole and that covers a foot of a shoe wearer, and a fastening member such as a shoelace that fastens the upper around the foot.
Recently, in a running shoe, high-grade cushioning properties and ride feelings during running are required and thus at the time of deformation of the sole moderate elastic elongation is necessary on the top surface of the sole.
In such a running shoe, when the shoe strikes onto the ground from the heel portion, in accordance with elongation of the sole top surface the bottom surface of the upper is also going to elongate in the longitudinal direction. As a result, the top portion of the upper is going to contract in the longitudinal direction. However, since the upper top portion in the prior-art shoe cannot contract in the longitudinal direction, the upper top portion is going to extend in the lateral direction thus causing a slack in the opening of the shoe. The result is that the opening of the shoe opens widely at the time of heel contact with the ground and a fit of the heel portion of the shoe relative to the foot heel portion decreases, which comes into question.
On the other hand, Japanese patent application publication No. 6-217806 (hereinafter called JP reference 6-217806) shows a shoe that is composed of a sole, an inside upper fixedly attached to the sole and receiving a foot of a shoe wearer, and a first and second strap extending along the outside of the inside upper on the medial and lateral side of the shoe. An end of the first and second strap is fixedly attached to the sole through a hole formed at the top portion of the heel rear end of the shoe and the other end of the first and second strap is connected to a shoelace.
In this case, by fastening the first and second strap via the shoelace, the opening of the inside upper of the shoe tightly contacts an ankle of the foot to increase a fit of the shoe.
In the shoe shown in JP reference 6-217806, it is possible in a degree to prevent the opening of the inside upper from opening at the time of heel contact with the ground by fastening the first and second strap extending around the opening of the inside upper. However, fastening of the first and second strap may hinder a free motion of the ankle.
The present invention has been made in view of these circumstances and an object of the present invention is to provide an upper structure for a shoe that can improve a fit of the heel portion of the shoe during the heel contact with the ground to the push off motion of the foot without hindering the free motion of the ankle.